High intensity short arc lamp



Oct. 27, 1964 N. c. BEESE HIGH INTENSITY SHORT ARC LAMP Filed March 15,1962 INVENTOR. NORMAN C. BEESE g. MM ATTORNEY United States Patent Ofiice 3,154,713 Patented Oct. 27, 1964 This invention relates toelectrical discharge lamps and more particularly to high pressure, highcurrent gas or vapor discharge short are lamps which are constructed toprovide desired acoustical resonance properties to be operative inoptical communications systems.

Lamps of the short are type are known to the prior art -2ihd in generalare constructed of a material capable of withstanding high temperaturesand to provide a chamber for gases, such as argon, xenon, neon, etc.,with or without mercury or other vapor additives, and within which arelocated electrodes for forming the arc.

Operation of short arc lamps on AC. power in the audio-frequency rangeor on D.C. power modulated by AC. currents may be affected by soundvibrations produced within the gas chamber which are caused by thermallyinduced variations in gas pressure that result from changes in currentdensity in the arc. At certain critical frequencies, acousticalresonance of appreciable intensity may be built up by reflections fromthe bulb walls causing distortion or instability of the are which oftenresults in extinction of the arc. In lamps of generally cylindricalshape, the critical frequencies are primarily caused by sound energyreflected from the ends of the lamp structure while in lamps ofspherical shape, the sound waves spread to the lamp walls and are thenfocused or directed back upon the arc to produce instability at theelectrodes.

The broad object of the invention is to provide a short arc lamp whichis constructed in a manner to eliminate or minimize the effect ofacoustical resonance on the arc stream when a resonant frequency is usedto operate or modulate the arc in order to permit the lamp to be usedover extended periods of time.

Another object of the invention is to provide a short are lamp in whichprovision is made to prevent deleterious acoustical resonance which isdeveloped when the lamp is operated or modulated by a resonant frequencyfrom interfering with the arc stream.

Another object of the invention is to absorb the deleterious acousticresonance developed when the lamp is operated or modulated by resonantfrequencies in order to prevent their interfering with the arc stream.

Another object of the invention is to equip one or both of the electrodestructures with a medium for absorbing deleterious acoustical resonancewhich is developed when the lamp is operated or modulated by a resonantfrequency.

Another object of the invention is to modify the lamp structure by theprovision of a zone therein for concentrating acoustical energy when thelamp is operated or modulated by resonant frequencies in order toprevent interferences with the arc stream.

Other and more detailed objects of the invention will become apparentfrom a better understanding of the invention, which may be had from theaccompanying drawings and description thereof.

FIG. 1 is a longitudinal sectional view of a short are lamp showing oneembodiment of the invention for absorbing acoustical vibrations andpreventing them from interfering with the arc stream;

FIG. 2 is a longitudinal sectional View showing a modification of FIG.1.

Referring to FIG. 1, a gaseous discharge lamp of the short arc type withwhich the present invention is adapted to be used is generallydesignated by the reference 10 and is constructed of clear fused quartzand provides strong wall structure for withstanding the hightemperatures and pressures encountered during operation. The lamp isshaped to provide a central envelope section 12 and outer sections 14-14which respectively are equipped to form the anode and cathode structuresof the lamp. The components for each of the anode and cathode structuresare generally similar and differ only in the particular design of theanode electrode 15 and the design of the cathode electrode 16. Since thecomponents of the anode and cathode structures are generally similar,only the anode section will be described in detail to provide anexplanation of the manner of assemblying the components and theirpositional arrangement within the lamp 10.

The anode electrode 15 is constructed of tungsten and is mounted at theinner end of a tungsten rod 17 while a quartz collar 18 is positioned onthe rod adjacent its outer end and the outer end is secured in a quartzcoupling block 19. Another tungsten rod 20 has its inner end secured inthe opposite end of the coupling block 19 While its outer end extendsthrough a glass closure 21 to receive leads 22 by means of a connector23. Conductors in the form of thin molybdenum ribbons 24 are suitablysecured about the rod 20 and extend along the coupling block 19 and arereceived between the first tungsten rod 17 and the collar 18. Afterassembling the anode components, as described, the outer section 14 ofthe quartz envelope is shrunk on to the coupling block 19 and collar 18to provide an integral structure; end closure 21 is secured to thesection 14 by means of a quartz to glass seal indicated at 25.

The quartz coupling block and quartz collar arrangement for mounting thetungsten conductors 17 and 20 provide strength to the lamp structureWhile the conductor ribbons 24 provide for the transmission of heavycurrent loads from the leads 22 to the anode electrode 15. In thedrawing the similar components of the cathode are identified similarlyto those of the anode.

In FIGS. 1 and 2, the discharge are between the anode 15 and cathode 16is shown located ofif the geometric center of the central section 12 ofthe lamp and toward the cathode section 14 of the lamp. Although this isa preferred lamp construction, it will be understood that the detailedstructure of the invention which will now be described has utility withlamps in which the discharge arc has a different location.

According to the present invention, improvement in the performance ofthe above disclosed lamp can be obtained by the provision of soundabsorbing means adjacent the electrode ends of the central section ofthe lamp and in the provision of an enlarged zone in the central sectionfor eliminating or minimizing acoustical resonant frequency when thelamp is operated or modulated.

In each of FIGS. 1 and 2, the central section 12 of the lamp is providedwith an enlarged circumferential bulge or protrusion 29 in generalalignment with the tip of cathode electrode 16. This bulge or protrusionis arcuate as shown and forms a zone which is transversely spaced fromthe discharge are and in which the reflected acoustical energy canbecome concentrated resulting in effect in the scattering of the primaryresonant frequency throughout the envelope and preventing it from beingreflected back to the arc stream as an echo phenomenon.

In FIG. 1, in addition to the bulge or protrusion 29 a disk or diaphragm30 is mounted transversely of the tungsten conductor rod 17 rearwardlyof the cathode 16 and adjacent the cathode end of the lamp centralsection. The diaphragm has its peripheral edge transversely spaced fromthe wall of the central section and also provides an axial space withthe collar 18. The axial space receives means for absorbing acousticalenergy in the form of a cylinder 31. Both'the disk or diaphragm 30 andthe cylinder 31 are preferably formed of thin material, for examplesheet metal, and are united to provide a unit which has apertures 32 inthe diaphragm and apertures 33 in the cylinder which admit the energyreflected from the walls of the lamp central section into the spaceformed by the unit; A lamp incorporating this sound absorbing elementgave good results and had only slight acoustical resonance below 12,000c.p.s. modulation. Although not shown in FIG. 1, the anode 15 of thelamp may be provided with a similar energy absorbing arrangement whichwould be disposed generally between the bushing 18 and 'the anode 15 ofthe anode section .14.

In the modification of FIG. 2, both the anode and cathode sections 14and 14' are shown provided with a somewhat different arrangement forabsorbing acoustical energy. A diaphragm or disk 40 which is similar insize and shape to the diaphragm or disk 30 but preferably is formed ofquartz is fixedly mounted about each of the tungsten conductors 17providing axial spaces at both the cathode and anode ends of the centralsection 12 with the collars 18. The spaces receive an energy absorbingmaterial such as quartz or wire wool 41 while the diaphragm 40 isprovided with apertures in a manner similar to that of diaphragm or disk30 of FIG. 1. The quartz or wire wool being porous provides along withthe disk an absorbent structure or unit having openings which permit thepassage of energy in a manner similar to that of the apertured disk andcylinder unit of FIG. 1.

'Both the sound wave absorbing constructions of FIGS. 1 and 2 providearrangements for the absorption of the reflected sound waves which arenot concentrated in the circular bulge 29. A lamp constructed as shownin FIG. 1 was operated at high power loading and showed only two feebleresonance frequencies when modulated below 12,000 c.p.s.

It should be understood that the foregoing disclosure shows onlypreferred embodiments of the invention and that it is intended to coverall modifications of the embodiments herein described which do notdepart from the spirit of the invention.

I claim:

1. An electric discharge lamp comprising a light transmissive centralchamber disposed between end electrode sections each having mountingstructure for a conductor, a first conductor extending axially of oneelectrode section and positioning an anode electrode within the centralchamber, a second conductor extending axially of the other electrodesection and positioning a cathode electrode Within the central chamber,said electrodes having their front ends spaced to provide an arcing gaptherebetween, a first rear space between the rear endof one electrodeand the mounting structure of one electrode section and a second rearspace between the rear end of the other electrode and the mountingstructure of the other electrode section, means for preventingacousticahenergy which is reflected from the walls of the centralchamber" from interfering with said arcing gap which comprises a unitformed of a perforated disk and an absorbing element, said perforated,disk being mounted in one of said rear spaces concentrically of oneconductor and said ab-' the absorbing element being formed of awool-likepack ing material. I

7 References Cited in the file of this patent UNITED STATES PATENTSKraus et a1. July 8, 1913 Beese Oct. 24, 1961

1. AN ELECTRIC DISCHARGE LAMP COMPRISING A LIGHT TRANSMISSIVE CENTRALCHAMBER DISPOSED BETWEEN END ELECTRODE SECTIONS EACH HAVING MOUNTINGSTRUCTURE FOR A CONDUCTOR, A FIRST CONDUCTOR EXTENDING AXIALLY OF ONEELECTRODE SECTION AND POSITIONING AN ANODE ELECTRODE WITHIN THE CENTRALCHAMBER, A SECOND CONDUCTOR EXTENDING AXIALLY OF THE OTHER ELECTRODESECTION AND POSITIONING A CATHODE ELECTRODE WITHIN THE CENTRAL CHAMBER,SAID ELECTRODES HAVING THEIR FRONT ENDS SPACED TO PROVIDE AN ARCING GAPTHEREBETWEEN, A FIRST REAR SPACE BETWEEN THE REAR END OF ONE ELECTRODEAND THE MOUNTING STRUCTURE OF ONE ELECTRODE SECTION AND A SECOND REARSPACE BETWEEN THE REAR END OF THE OTHER ELECTRODE AND THE MOUNTINGSTRUCTURE OF THE OTHER ELECTRODE SECTION, MEANS FOR PREVENTINGACOUSTICAL ENERGY WHICH IS REFLECTED FROM THE WALLS OF THE CENTRALCHAMBER FROM INTERFERING WITH SAID ARCING GAP WHICH COMPRISES A UNITFORMED OF A PERFORATED DISK AND AN ABSORBING ELEMENT, SAID PERFORATEDDISK BEING MOUNTED IN ONE OF SAID REAR SPACES CONCENTRICALLY OF ONECONDUCTOR AND SAID ABSORBING ELEMENT SURROUNDING THE CONDUCTOR ANDEXTENDING FROM THE DISK TO THE MOUNTING STRUCTURE OF THE ELECTRODESECTION.